The present invention relates to posture supports and, in particular, to a support which is integrally adaptable to a chair back or separately mountable as an accessory item to the backrest of a variety of available chairs and wherein each of a pair of thoracic and pelvic-sacral support cushions are independently adjustable along a plurality of planar axes by the seated occupant.
With a growing awareness and appreciation of the ergonomics of the work place has come an attempt to design improved furnishings to facilitate the use of computers, drafting tables, motor vehicles and the like by the seated worker. Various of these designs seek to promote proper posture and thereby prolong the duration of meaningful equipment usage.
A variety of chair constructions and seating accessories have particularly evolved for supporting the spine of the seated occupant. Most of such endeavors have been directed to providing non-adjustable assemblies which promote a specific seating posture for each particular chair construction. That is, most typically, such designs provide for a single rigid convex backrest cushion which is secured to a reclined frame to support the lumber spine. Such constructions, however, do not promote any particular spinal posture when leaning forward. Nor do such constructions provide for a combination of support surfaces that accommodate a variety of seating postures; nor do they permit adjustment while seated.
In the above regard, Applicant is particularly aware of a number of single cushion support constructions shown in U.S. Pat. Nos. 2,060,298; 2,838,099; 2,831,533; 3,348,880; and 4,190,286. Various of these supports adjustably mount to a chair back and provide a mechanism for vertically positioning the cushion with the user's lumbar spine. One of these supports also provides for inflatable pneumatic cushions.
Applicant is also aware of other backrest supports which provide for a pair of support cushions for simultaneously supporting two regions of the back. These assemblies are shown in U.S. Pat. Nos. 567,096; 1,007,985; and 3,880,463 and in articles by E. H. Bradford and J. S. Stone, "The Seating of School Children", Transactions of the American Orthopedic Association, 12: 170-183 (1899) and by F. J. Cotton, "School Furniture for Boston Schools", American Physical Education Review, 9:267-284 (1904). Of these, probably the most relevant to the present invention is the assembly shown in U.S. Pat. No. 3,880,436. There, a pair of cushions are permanently mounted in fixed spatial relation to one another along an inner support frame which, in turn, is pivotally mounted to an outer frame. The cushions are vertically adjustable as a unit and may also be rotated or tilted as a unit. Otherwise, the cushions are not independently adjustable relative to one another or the inner frame, nor is either cushion separately tiltable. Thus the assembly provides only for a limited fitting to the user.
One other patent of which Applicant is aware, U.S. No. 2,304,349, shows a single cushion auxiliary backrest wherein the cushion adjusts both vertically and horizontally to contact the "small" or lumbar vertebrae of the user's back. Vertical adjustment is achieved with a spring loaded slide bracket, while horizontal adjustment is achieved with a pair of clamped ears which mount above a pivot stem. A tilting action is obtained with rotation of the clamp ears about a pivot pin and an extendible stop that strikes the cushion back.
To the extent applicant is aware of other references showing features directed to the concerns which are alleviated by way of the present invention, Applicant's own book, D. Zacharkow, Posture: Sitting, Standing, Chair Design and Exercise (Springfield, Thomas, 1988) discusses the need for a new support mechanism. Applicant is also aware of an article by Rizzi, M., "Entwicklung eines Verschiebbaren Ruckenprofils fur Auto-und Ruhesitze," appearing on pp. 112-119 in E. Grandjean, Proceedings of the Symposium on Sitting Posture (London, Taylor and Francis, 1969).
In contrast to the above noted art, the present invention seeks to provide a seating posture which mimics a preferred standing posture to not only erectly support the spinal column when seated, but also to reinforce and carry over this posture to standing movements. That is, the proper axial relationship of the thorax and pelvis in upright standing involves the upper trunk being brought over or slightly anterior to the hips. This posture is achieved through proper extension of the lower thoracic spine and thoracolumbar junction (i.e. ninth thoracic vertebra through first lumbar vertebra) and results in activation of the lower abdominal muscles, along with a beneficial increase in the resting intra-abdominal pressure.
This increase in intra-abdominal pressure is beneficial for the following reasons:
(1) It promotes proper diaphragmatic excursion and respiration. PA1 (2) It raises the ribs and chest to their most optimal position. PA1 (3) It prevents stagnation of the circulation in the splanchnic region. PA1 (4) It provides stabilization of the trunk. PA1 (5) It reduces spinal stress to the thoracic and lumbar spine by both lengthening and extending the spine. A secondary effect is that the cervical spinal posture is improved. PA1 (1) Slumped sitting postures with the thoracolumbar spine in flexion. This frequently occurs both when leaning forward, such as over a desk, and in most reclined postures. PA1 (2) sitting with a convex lumbar support that moves the lumbar spine into lordosis. Such a sitting posture will result in a posterior trunk lean, with the upper trunk being brought posterior to the hips. PA1 (b 3) Conventional backrest designs that include a high, inclined backrest, but without proper lower thoracic support to promote extension. PA1 (b 4) A forward inclination to the upper backrest, thereby pushing the shoulders forward and increasing thoracic flexion. PA1 (5) Inadequate space just above the seat for the posterior placement of the buttocks and clothing, thereby preventing the hips from being pushed back.
As opposed to the above beneficial posture, the most common standing postural fault involves a posterior trunk lean, with the upper trunk being displaced posterior to the hips. Such a posture results in relaxation of the lower abdominals and a decrease in intra-abdominal pressure.
Similarly, in a sitting position, relaxation of the lower abdominals and a decrease in intra-abdomimal pressure results from: